Adsorption and elution of metal from ion exchange resin

Abstract

Method and apparatus (10) includes the use of multiple containers (B-1-B-3) containing a weak base ion resin (R) through which plating rinse water (W) is pumped with precious metal such as potassium gold cyanide adsorbed by said resin and then with the cyanide sequentially eluted by potassium hydroxide, water, potassium thiocyanate, water, and the resulting effluent evaporated (at 40) and then chilled (at 44) to remove for reuse the gold and inorganic salt and base.

We claim: 
     
       1. A method of recovering gold present in the form of gold salts having gold-cyanide anions from rinse water comprising the steps of: providing a macroporous weak-base anion resin having sulfate anions adsorbed therein;   pumping said rinse water through said resin to exchange said gold-cyanide anions for said sulfate anions adsorbed in said resin thereby producing a gold loaded resin;   eluting a first portion of said gold-cyanide anions from said gold loaded resin with an aqueous solution of an inorganic base thereby producing a first eluent solution;   eluting a second portion of said gold-cyanide anions from the said gold loaded resin with an aqueous solution of an inorganic salt thereby producing a second eluent solution, and a regenerated anion resin, said regenerated resin being capable of being reused for absorbing sulfate anions;   removing said gold cyanide anions in the form of gold cyanide salts from said first and second eluent solutions by separately evaporating water from said resultant first and second eluent solution to a point of approaching saturation of a gold cyanide salt formed in said separate first and second eluent solutions to crystalize first and second portions of said gold cyanide salts from said inorganic base and inorganic salt solution;   recovering said crystallized gold salts; and   recovering said inorganic base and salt solutions which are capable of being reused.   
     
     
       2. The method of claim 1 wherein said step of providing a resin having sulfate anions adsorbed therein includes to step of rinsing a free base form of a macroporous resin with sulfuric acid followed by a water rinse to remove any excess sulfuric acid. 
     
     
       3. The method of claim 1 wherein said inorganic base solution is a one molar potassium hydroxide solution and said inorganic salt solution is a one molar potassium thiocyanate solution. 
     
     
       4. The method of claim 1 wherein said resin is a tertiary amine. 
     
     
       5. The method of claim 1 wherein a free base form of a macroporous resin is flooded with a 5 percent solution of sulfuric acid whereby said acid is adsorbed on said resin thereby providing said sulfate anions. 
     
     
       6. A method of recovering gold present in the form of gold salts having gold-cyanide anions from rinse water comprising the steps of: providing a plurality of bed column containers each charged with macroporous weak-base anion exchange resin having sulfate anions adsorbed therein;   pumping said rinse water through a first container of said resin to exchange said gold-cyanide anions therein for said sulfate anions adsorbed in said resin and thereby producing a first gold loaded resin, said rinse water being pumped through said first container to a point of exhaustion of said anion exchange resin as defined by the presence of gold-cyanide ions in discharge water from said first container;   shifting flow of said rinse water to a second container to continue the exchange of said gold-cyanide anions from said rinse water to said resin, thereby producing a second gold loading resin;   regenerating a macroporous weak base anion exchange resin in said first column by the steps of:   eluting a first portion of said gold-cyanide anions from said first gold loaded resin with an aqueous solution of an inorganic base thereby producing a first eluent solution and a partially regenerated resin;   eluting a second portion of said gold-cyanide anions from said partially regenerated first resin with an aqueous solution of an inorganic salts thereby producing a second eluent solution, and a regenerated resin; and   removing said gold cyanide anions in the form of gold cyanide salts from said first and second eluent solutions by the steps of:   separately evaporating water from said resultant first and second eluent solutions to a point approaching saturation of a gold cyanide salt formed in said separate first and second eluent solutions;   separately chilling said evaporated first and second separate solutions,   crystallizing first and second portions of said gold cyanide salts from said inorganic base and inorganic salt solutions; and   recovering said crystallized gold salts; and   recovering said inorganic base and salt solutions which are capable of being reused.   
     
     
       7. An apparatus operable to recover gold dragout from plating and stripping operations, said gold being present in the form of gold salts having gold-cyanide anions from rinse water utilized in plating and stripping operations, the apparatus including: at least one container means defining a bed column for an ion exchange resin, said at least one container being charged with a macroporous weak-base anion resin having sulfate anions adsorbed therein;   means interconnected to said at least one column and operable to pump rinse water therethrough;   means connected to said at least one column adapted to detect the presence of gold cyanide flowing from said bed column as an indication of exhaustion of said resin;   means selectively interconnectable to said at least one column for providing at least two solutions for separately eluting said gold-cyanide anions from said at least one column, a first eluent being an aqueous inorganic base solution and a second eluent being an aqueous inorganic salt solution;   means including first and second further containers for separately collecting respective first and second eluent solutions each having respective first and second portions of said gold-cyanide anions therein;   means to separately evaporate water from said resultant first and second eluent solutions to a point approaching saturation of a gold cyanide salt formed in said separate first and second eluent solutions;   means for separately chilling said evaporated first and second separate solutions to crystalize first and second portions of said gold cyanide salt from said inorganic base and inorganic salt solutions; and   means for receiving said crystallized gold salts.   
     
     
       8. The apparatus of claim 7 wherein said bed columns include a series of containers and means are provided to switch flow of said rinse water and said eluent solutions from one container to the next to facilitate recovery of gold cyanide anions in the said container upon exhaustion of the said resin through adsorption of the gold cyanide anions therein. 
     
     
       9. The apparatus of claim 7 including a plurality of pipes interconnecting said one column and said solutions, said column having a series of valves adapted to regulate flow of said rinse water and eluent solutions and control means for controlling operation of said valves to provide a sequenced operation. 
     
     
       10. The apparatus of claim 9 wherein said control means is a microprocessor.